Development of Maize Hybrids With Enhanced Vitamin-E, Vitamin-A, Lysine, and Tryptophan Through Molecular Breeding

Abstract

Malnutrition is a widespread problem that affects human health, society, and the economy. Traditional maize that serves as an important source of human nutrition is deficient in vitamin-E, vitamin-A, lysine, and tryptophan. Here, favorable alleles of vte4 (α-tocopherol methyl transferase), crtRB1 (β-carotene hydroxylase), lcyE (lycopene ε-cyclase), and o2 (opaque2) genes were combined in parental lines of four popular hybrids using marker-assisted selection (MAS). BC₁F₁, BC₂F₁, and BC₂F₂ populations were genotyped using gene-based markers of vte4, crtRB1, lcyE, and o2. Background selection using 81-103 simple sequence repeats (SSRs) markers led to the recovery of recurrent parent genome (RPG) up to 95.45%. Alpha (α)-tocopherol was significantly enhanced among introgressed progenies (16.13 μg/g) as compared to original inbreds (7.90 μg/g). Provitamin-A (proA) (10.42 μg/g), lysine (0.352%), and tryptophan (0.086%) were also high in the introgressed progenies. The reconstituted hybrids showed a 2-fold enhancement in α-tocopherol (16.83 μg/g) over original hybrids (8.06 μg/g). Improved hybrids also possessed high proA (11.48 μg/g), lysine (0.367%), and tryptophan (0.084%) when compared with traditional hybrids. The reconstituted hybrids recorded the mean grain yield of 8,066 kg/ha, which was at par with original hybrids (mean: 7,846 kg/ha). The MAS-derived genotypes resembled their corresponding original hybrids for the majority of agronomic and yield-related traits, besides characteristics related to distinctness, uniformity, and stability (DUS). This is the first report for the development of maize with enhanced vitamin-E, vitamin-A, lysine, and tryptophan.

Keywords: DUS traits; biofortication; hybrid; maize; marker-assist selection; nutrition.

Figure 1

Background recovery of selected progenies in BC₂F₂ of the RP × DP [(A) HKI161-VA+VE, (B) HKI163-VA+VE, (C) HKI193-1-VA+VE, and (D) HKI193-2-VA+VE]; 1, recurrent parent (red); 2, donor parent (blue); light green color represent the locus in heterozygous condition; light red color in “consensus sequence” represents the locus having donor allele or heterozygosity, 3–5/6: introgressed progenies; favorable allele of vte4 (green box), favorable allele of phi057 (yellow box), favorable allele of lcyE (purple box), favorable allele of crtRB1 (pink box); group 1–10 represents the chromosome 1–10.